JP5078532B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus that is mounted on an image forming apparatus and corrects skew while conveying a sheet.

  Sheets mounted on the image forming apparatus and continuously fed at a short conveyance interval (interval between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet) are successively moved along the reference plane while being conveyed at high speed. Thus, a sheet conveying apparatus that corrects skew is put into practical use.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a sheet conveying device disposed on the upstream side of a toner image transfer portion of an electrophotographic image forming apparatus. Here, a reference member having a reference surface parallel to the sheet conveyance direction is disposed on the side of the sheet conveyance path, and a plurality of skew rollers are disposed on the side close to the reference surface. Then, the plurality of skew rollers move the sheet to the reference surface side while conveying the sheet, and convey the sheet so that the side of the sheet hits the reference surface. In addition, the sheet whose skew has been corrected on the reference plane is moved to a predetermined position in a direction perpendicular to the sheet conveyance direction by a positioning roller that is arranged on the downstream side of the reference plane and is movable in a direction perpendicular to the sheet conveyance direction. Is done.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a sheet conveying device arranged on a conveyance path for backside printing of an electrophotographic image forming apparatus. Here, the second skew roller is disposed at a position far from the reference surface on the upstream side of the first skew roller disposed on the side close to the reference surface. The second skew roller has a skew amount set equal to that of the first skew roller, and prevents rotation around the center of gravity of the sheet when the first skew roller starts conveying the sheet.

  In Patent Document 3, the sheet surface is arranged on the upstream side of the first skew roller contacting the sheet surface on the side closer to the reference surface than the center line of the sheet parallel to the sheet conveying direction, and on the side farther than the same center line. A sheet conveying apparatus is shown in which a second skew roller that abuts is disposed.

JP-A-11-189355 Japanese Patent Laid-Open No. 2003-146489 Japanese Patent Laying-Open No. 2005-104712

  In recent years, with the expansion of applications of image forming apparatuses, there is a demand for image formation on special sheets that are significantly different from conventional plain paper and coated paper in weight, friction coefficient, size, conveyance posture, and the like.

  In such a sheet conveying apparatus shown in Patent Documents 1 to 3, when such a sheet is obliquely fed and moved toward the reference surface, the upstream skew roller conveys the sheet and contacts the downstream skew roller. The seat posture becomes unstable during this time.

  Although details will be described later as a comparative example, the sheet rotates around the upstream skew roller during a period in which the sheet is conveyed only by the upstream skew roller. In the case of a sheet having a large lower surface friction coefficient, a light weight, and a short length in the direction along the reference surface, the rotation angle becomes large and a large skew amount is likely to be generated. If the skew amount becomes too large, there is a possibility that the skew correction of the sheet may not be completed by the downstream skew roller disposed near the reference surface before passing through the reference surface.

  In other words, as shown in Patent Documents 2 and 3, even if an intentional rotation of the sheet is generated to approach the reference surface quickly, the intended rotation cannot be generated on the sheet, and instead the reference surface is returned to the reference surface. It makes it difficult to gather.

  In addition, the skew roller can be used even when a plurality of sheets are skewed so that the skewed sheet does not interfere with sheet skew correction or float the sheet surface in the process of following the reference surface. It is designed to allow the seat to rotate with slippage between the surfaces. For this reason, even if the sheet is being fed obliquely by a pair of upstream and downstream skew feeding rollers, if the sheet conveyance resistance is biased due to friction with the guide surface of the sheet, the sheet rotates and is conveyed. Becomes unstable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus capable of correcting skew feeding reliably by removing instability of a sheet conveying posture by using members and controls common to various sheets.

  The sheet conveying apparatus according to the present invention is disposed along the sheet conveying direction, and a reference member that slides in contact with the sheet and aligns the sheet, and a first member that rotates in contact with the sheet and obliquely feeds the sheet toward the reference member. A skew feeding rotor, and a position upstream of the first skew feeding rotor and farther from the reference member than the first skew feeding rotor, at a central position of the sheet in a direction perpendicular to the sheet conveying direction. A second skew feeding rotating body that is arranged correspondingly and rotates in contact with the sheet and obliquely feeds the sheet toward the reference member; and an approach / separation mechanism that contacts and separates the second skew feeding rotating body from the sheet; And the second skew feeding rotator is turned into a sheet at a timing when the sheet conveyed in the sheet conveying direction with the second skew feeding rotator separated from the sheet reaches the first skew feeding rotator. The contact / separation mechanism is controlled to contact And wherein the door.

  In the sheet conveying apparatus of the present invention, the second skew feeding rotator is separated from the sheet until the sheet reaches the first skew feeding rotator, so that the sheet is conveyed only by the second skew feeding rotator. Little rotation of the sheet occurs.

  Then, the second skew feeding rotating body comes into contact with the center position of the sheet in the direction perpendicular to the sheet conveying direction to feed the sheet obliquely, so the moment of frictional resistance on the guide surface of the sheet around the contact position is reduced. As a result, the component force (swivel component) for rotating the seat is reduced. The center position means a region that is not greatly deviated in one of the directions perpendicular to the sheet conveying direction.

  Therefore, it is possible to reliably perform skew correction using various common members and controls for various types of sheets having different weights, friction coefficients, sizes, conveyance postures, and the like as compared with conventional sheets.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. The present invention is another implementation in which part or all of the configuration of each embodiment is replaced with an alternative configuration as long as the distance between the upstream skew roller and the reference surface changes according to the sheet size. It can also be implemented in the form.

  Accordingly, the present invention can be implemented not only in the electrophotographic image forming apparatus but also in various image forming apparatuses such as an offset printing system and an ink jet system. The electrophotographic method is not limited to the tandem method in which a plurality of image forming units are arranged side by side, but can also be implemented by a rotary method in which the image forming units are arranged in a cylindrical shape. The present invention is not limited to the intermediate transfer method in which the image is primarily transferred to the intermediate transfer member and then secondarily transferred to the sheet, but can also be implemented by a direct transfer method in which the toner image is directly transferred from the photosensitive member to the sheet.

  In addition, about the general matter of the sheet conveying apparatus shown by patent documents 1-3, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<First Embodiment>
FIG. 1 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus according to the first embodiment.

  As shown in FIG. 1, an image forming apparatus 60 according to the first embodiment is an intermediate transfer tandem type full-color printer multifunction machine in which four-color image forming units using an electrophotographic method are arranged on a linear portion of an intermediate transfer belt 606. is there.

  The intermediate transfer method does not require the sheet to be held on a transfer drum or a transfer belt unlike the direct transfer method, and thus can cope with a wide variety of sheets such as thick paper and coated paper. The intermediate transfer tandem method is suitable for realizing high productivity due to the features of parallel processing in a plurality of image forming units and batch transfer of full-color images.

  The sheet S is stored in a form that is stacked on a lift-up device 62 included in the paper feeding device 61, and is fed by the paper feeding unit 63 in accordance with the image formation timing.

  Here, the paper feeding unit 63 includes a method using frictional separation by a paper feed roller or the like, a method using air separation and adsorption, and the like. In the first embodiment, a paper feeding method using air is used. Yes.

  The sheet S sent out by the paper feed unit 63 passes through a transport path 64a of the transport unit 64 and is transported to a skew feeding registration apparatus (hereinafter referred to as a registration apparatus) 65 according to the present invention. The skew feeding registration device 65 feeds the sheet S to the secondary transfer unit after performing skew feeding correction of the sheet S and timing correction for matching the toner image formed on the intermediate transfer belt 606 with the sheet.

  The secondary transfer portion is formed by pressing the secondary transfer outer roller 66 against the intermediate transfer belt 606 supported by the secondary transfer inner roller 603. The secondary transfer unit transfers the toner image on the intermediate transfer member 606 to the sheet S by superimposing the intermediate transfer belt 606 on the passing sheet S and applying a predetermined pressure and transfer electric field.

  Along the intermediate transfer belt 606, four image forming portions 613 for forming toner images of yellow (Y), magenta (M), cyan (C), and black (Bk) are arranged. Since the four image forming units 613 are configured in common with different colors of toner filled in the developing device 610, the most upstream yellow (Y) image forming unit 613 will be described. Note that the number of colors is not limited to four, and the color arrangement order is not limited to this.

  In the image forming unit 613, a charging device (not shown), an exposure device 611, a developing device 610, a primary transfer device 607, and a photoconductor cleaner 609 are arranged around a photoconductor 608 that rotates in the direction of arrow a in the drawing.

  The exposure device 611 scans and exposes the surface of the photoconductor 608 uniformly charged by the charging device with a laser beam modulated by image data via a mirror 612 to generate an electrostatic latent image of the image. Write.

  The developing device 610 forms a toner image on the photosensitive member 608 by developing the electrostatic latent image formed on the photosensitive member 608 by electrostatically attaching toner.

  The primary transfer device 607 sandwiches the intermediate transfer belt 606 with the photoconductor 608 to form a primary transfer portion, and applies a predetermined pressure and transfer electric field to the toner image to intermediate the toner image on the photoconductor 608. Transfer is performed on the transfer belt 606.

  The photoconductor cleaner 609 collects the transfer residual toner slightly remaining on the surface of the photoconductor 608 that has passed through the primary transfer portion, and prepares the photoconductor 608 for the next image formation.

  The intermediate transfer belt 606 is stretched by a drive roller 604, a tension roller 605, and a secondary transfer inner roller 603, and is rotationally driven in the direction of arrow b in the drawing.

  The Y, M, C, and Bk image forming units 613 process the image forming processes of the respective colors in parallel at the timing of superimposing them on the upstream color toner image transferred to the intermediate transfer belt 606. As a result, a full-color toner image is finally formed on the intermediate transfer belt 606 and conveyed to the secondary transfer unit.

  Then, as described above, the full-color toner image is transferred to the sheet S fed to the secondary transfer unit, and then the sheet S is conveyed to the fixing device 68 by the pre-fixing conveyance unit 67.

  The fixing device 68 melts and fixes the toner image on the sheet S by applying a predetermined pressure by an opposing roller or belt or the like and generally heating by a heat source such as a heater.

  The sheet S on which the fixed image is formed is discharged as it is onto the discharge tray 600 through the branch conveyance device 69. However, when double-sided image formation is required, the branch conveyance device 69 switches the conveyance path and conveys the sheet S to the reverse conveyance device 601.

  The reverse conveying device 601 conveys the sheet S to the double-sided conveying device 602 with the leading and trailing ends switched. Thereafter, in synchronization with the interval of the sheet S of the subsequent job conveyed from the sheet feeding device 61, the conveyance unit 64 merges the sheets S for double-sided image formation through the refeed path 64b to the secondary transfer unit. To feed. The image forming process for the back surface (second surface) is the same as that for the front surface (first surface) described above, and is therefore omitted.

  The switchback method is a relatively easy configuration as a method of switching the front and back of the seat S, and is advantageous in terms of space. However, in the switchback method, the leading and trailing edges of the sheet S are interchanged through reversal, so it is necessary to set a common reference side for positioning the front and back images in a direction perpendicular to the sheet conveying direction. For this reason, the skew feeding registration device 65 positions the transfer positions of the front and back toner images by correcting the skew feeding by making one side of the sheet S follow a reference plane parallel to the sheet conveyance direction.

  By the way, in a sheet conveying apparatus that conveys a sheet, the skew or misalignment of a sheet that occurs during conveyance is poor in delivery with a conveyance jam or other equipment, or when printing is performed on the sheet surface, the printing accuracy is low. This causes problems such as degradation. The case of the conveyance path provided in the image forming apparatus does not fall into this example, and further consideration is required when the position accuracy of the image formed on the sheet surface, especially when image formation is performed on the front and back surfaces of the sheet. Become.

  Accordingly, the image forming apparatus 60 includes the skew feeding registration device 65 immediately before the secondary transfer portion on which an image is formed on the sheet surface, and the skew feeding and misregistration accumulated in the long transport path from the paper feeding device 61. To obtain a high image position accuracy. The skew feeding registration device 65 feeds the sheet obliquely while conveying the sheet at high speed so that the side of the sheet is brought into contact with the reference member 71 (FIG. 2) and the side edge of the sheet is parallel to the sheet conveying direction. Align (side edge alignment).

  The skew feeding registration device 65 may be applied to a high-end machine at a printing press level because a product having excellent image position accuracy can be obtained. However, in the case of such a high-end machine, there are many cases where it is necessary to deal with a wide variety of seats at the same time. For this reason, sufficient side-end alignment performance is stably achieved through a huge combination of various parameters such as sheet size, thickness, weight, friction coefficient, and smoothness, and environmental parameters such as temperature and humidity. We need to be able to do it.

<Example 1>
2 is a plan view of a conveyance unit including the skew feeding registration apparatus according to the first embodiment, FIG. 3 is an explanatory diagram of a drive mechanism of the skew feeding registration apparatus, FIG. 4 is a flowchart of conveyance control, and FIG. It is explanatory drawing.

  As shown in FIG. 2, the skew feeding registration device 65 receives the sheet conveyed in the sheet conveyance direction indicated by the arrow A from the upstream pre-registration conveyance unit 64 </ b> R, and receives the downstream secondary transfer unit. 66P. The skew feeding registration device 65 transports the sheet, which has been skew-corrected and side-aligned by the skew feeding registration portion 65P, by a predetermined amount in the direction perpendicular to the sheet transport direction by the slide portion 65R, and transports the sheet to the secondary transfer outer roller 66. Position in the axial direction.

  The pre-registration conveyance unit 64R conveys a sheet placed on the plane of the conveyance guide 75 in the direction of arrow A by the pre-registration conveyance rollers 73 and 74. The pre-registration transport rollers 73 and 74 rotate in contact with a driven roller (not shown) through an opening formed in the transport guide 75 (see FIG. 1). The pre-registration conveyance unit 64R and the skew feeding registration unit 65P are central reference sheet conveyance apparatuses in which a conveyance reference is set on a center line along the sheet conveyance direction.

  The pre-slope feeding roller 12 is disposed on the center line along the sheet conveyance direction of the sheet conveyance path, and obliquely feeds the sheet delivered from the pre-registration conveyance roller 73 and moves toward the abutting reference member 71. Let The distance in the sheet conveyance direction from the nip of the most upstream skew feeding roller 70a to the nip of the pre-slope feeding roller 12 is set to a distance D1. Details of the distance D1 will be described later.

  The skew feeding registration unit 65P feeds the sheet placed on the movable guide 11 and the fixed guide 10 obliquely by the skew feeding rollers 70a, 70b, and 70c, and slides the side edge of the sheet to the reference member 71. Align side edges.

  The skew feeding registration portion 65P includes a movable unit 11U in which the movable guide 11, the skew feeding rollers 70a, 70b, and 70c, and the abutting reference member 71 are integrated, and a fixed unit 10U that includes the fixed guide 10. The movable unit 11U waits for a sheet conveyed by the pre-registration conveyance rollers 73 and 74 while moving to a position corresponding to the sheet size.

  The conveyed sheet is obliquely fed by the pre-slope feeding roller 12 and the oblique feeding rollers 70a, 70b, and 70c, and comes into contact with an abutting reference member 71 which is an example of a reference member.

  The slide portion 65R includes a conveyance guide 79, a slide roller 7, a pre-slide sensor 77, and a post-slide sensor 78. The slide roller 7 slides in the direction of arrow B while rotating, and aligns the thrust position of the sheet whose skew has been corrected in the skew feeding registration portion 65P with the image position on the intermediate transfer belt (606: FIG. 1).

  The secondary transfer portion 66P includes a secondary transfer outer roller 66, a secondary transfer inner roller (603: FIG. 1), and an intermediate transfer belt (606: FIG. 1). The transfer timing with the toner image on the intermediate transfer belt (606: FIG. 1) is adjusted by controlling the arrival timing of the leading edge of the sheet based on the detection signal of the post-slide sensor 78.

  As shown in FIG. 3, the skew feeding rollers 70 a, 70 b, and 70 c are arranged as close to the abutting reference member 71 as possible. This position is a position where the sheet can be prevented from buckling and rising when the sheet is pressed against the abutting reference member 71. In addition, if the gap between the sheet nipped by the skew feeding rollers 70a, 70b, and 70c and the abutting reference member 71 is wide, the sheet passes through the abutting reference member 71 without completing the side edge alignment. is there.

  The skew feeding rollers 70 a, 70 b, 70 c, which are examples of the first skew feeding rotating body, are provided with a fixed positional relationship with respect to the abutting reference member 71, and are respectively driven through an opening 11 h formed in the movable guide 11. It contacts the rollers 70i, 70j, 70k. The driven rollers 70 i, 70 j, 70 k have a smaller frictional force than the skew feeding rollers 70 a, 70 b, 70 c, and the contact height is set slightly higher than the plane of the movable guide 11.

  The pre-slope feeding roller 12, which is an example of a second skew feeding rotating body, is configured in the same manner as the slope feeding rollers 70a, 70b, and 70c, and contacts the driven roller 12j through an opening 75h formed in the conveyance guide 75. The driven roller 12j has a smaller frictional force against the sheet than the pre-slope feeding roller 12, and the contact height is set slightly higher than the plane of the conveyance guide 75.

  However, the skew feeding rollers 70a, 70b, 70c and the pre-slope feeding rollers have a friction coefficient and a cross-sectional shape so that the sheet can rotate following the abutting reference member 71 even when a plurality of the skew feeding rollers are skew feeding. Designed.

  The oblique feeding rollers 70a, 70b, 70c, the pre-slope feeding roller 12, the pre-registration conveying rollers (73, 74: FIG. 2), and the slide roller (7: FIG. 2) are driven to rotate by the motor M3, and are moved in the direction of arrow A. Given equal transport speed.

  The oblique feeding rollers 70a, 70b, 70c, the pre-slope feeding roller 12, and the pre-registration conveying rollers (73, 74: FIG. 2) are driven up and down by a motor M2, which is an example of a contact / separation mechanism, and driven rollers 70i, 70j. , 70k, 12j, etc.

  However, when the skew feeding rollers 70a, 70b, 70c and the pre-slope feeding roller 12 descend and come into contact with the sheet, the pre-registration conveyance rollers (73, 74: FIG. 2) are separated from the sheet.

  The movable unit 11U is driven by the motor M1 which is an example of the first adjusting means and moves in the direction of arrow C, and the abutting reference member 71 which is an example of the reference member is moved in the sheet width direction with respect to the pre-slope feeding roller 12. The distance is set according to the sheet size.

  As shown in FIG. 4 with reference to FIG. 2 and FIG. 3, when the pre-registration conveyance sensor 76 detects the leading edge of the sheet, the control unit 9 which is an example of a control unit temporarily stops at the pre-registration conveyance roller 73. This is for resetting the accumulated error of the leading passage timing that occurs during the long conveyance path.

  The control unit 9 acquires the sheet size (S11), and obtains a distance D2 from the nip of the skew feeding rollers 70a, 70b, 70c to the nip of the pre-slope feeding roller 12 in the sheet width direction. The distance D2 is set to almost half of the size in the width direction according to the sheet size (including vertical / horizontal feed) of the conveyed sheet.

  The control unit 9 controls the motor M1 to move the movable unit 11U in the direction of arrow C (sheet width direction), and waits at a distance D2 between the skew feeding rollers 70a, 70b, 70c and the pre-slope feeding roller 12. (S12).

  The controller 9 controls the motor M3 to start sheet conveyance by the pre-registration conveyance rollers 73 and 74 (S13).

  After starting conveyance by the pre-registration conveyance rollers 73 and 74, the control unit 9 determines whether or not the sheet reaches the skew feeding roller 70a based on a timer count or the like (S14).

  The controller 9 controls the motor M2 at the timing when the leading edge of the sheet reaches the skew feeding roller 70a (YES in S14), and lifts the pre-registration conveyance rollers 73 and 74 to release the sheet nip (S15). . This is because if the sheet is nipped, even if the skew feeding roller 70a starts skew feeding, the sheet advances straight and is not skewed. At the same time, the pre-slope feeding roller 12 descends, nips the center of the sheet and starts skew feeding, and after a little delay, the skew feeding roller 70a nips the edge of the sheet and starts conveyance. This is because the rotation of the sheet when the skew feeding roller 70a starts conveying can be prevented by the nip force of the pre-slope feeding roller 12.

  Initially, the sheet is obliquely fed by the pre-slope feeding roller 12 and the skew feeding roller 70a (S16), and then the oblique feeding rollers 70b and 70c sequentially feed the sheet. The sheet is obliquely fed toward the abutting reference member 71, rotated so that the entire side along the sheet conveying direction follows the abutting reference member 71, and skew correction and side edge alignment are performed (S17). ).

  When the pre-slide sensor 77 detects the leading edge of the sheet, the control unit 9 determines that the sheet has reached below the slide roller 7 (S18).

  When the sheet reaches below the slide roller 7 (YES in S18), the control unit 9 controls the motor M2, which is an example of a contact / separation mechanism, to raise the pre-slope feeding roller 12 and the slope feeding rollers 70a, 70b, and 70c. Thus, the sheet nip is opened (S19). This is because if the slide roller 7 is slid while the rollers are nipped, the sheet rotates and becomes oblique.

  The controller 9 slides the slide roller 7 in the arrow B direction to move the sheet to a position that matches the toner image on the intermediate transfer belt 606 (S20).

  Accordingly, the sheet is conveyed to the secondary transfer unit (S21).

  The control unit 9 repeats the control of S11 to S22 until the job is completed (NO in S22).

  FIG. 5 illustrates the state of each stage corresponding to S13 to S17 in FIG. 4, and takes as an example a case where the length in the sheet conveyance direction is twice the distance D1 described above.

  FIG. 5A shows a state immediately after the sheet is temporarily stopped by the pre-registration conveyance roller 73 and then conveyed again. At this stage, the pre-slope feeding roller 12 is in a state in which the nip is released, and the sheet S is conveyed in the direction of arrow A by the conveyance force F <b> 1 received from the pre-registration conveyance roller 73.

  FIG. 5B shows a state where the leading edge of the sheet S has reached the nip portion of the registration roller 70a. At this time, the nips of the pre-registration conveyance rollers 73 and 74 are released, and at the same time, the nip of the pre-slope feeding roller 12 is formed, and the sheet S is sandwiched between the two rollers of the skew feeding roller 70a and the pre-slope feeding roller 12. Be transported.

  The relationship of the force at this time will be considered. Here, it is assumed that the frictional resistance force R on the conveyance guide 75 with respect to the conveyance force F3 of the skew feeding roller 70a is concentrated on the center of gravity of the sheet S.

  For this reason, if the sheet length in the sheet conveyance direction = twice the distance D1, the conveyance force F2 by the pre-slope feeding roller 12 acts on the center of gravity of the sheet S, so the frictional resistance force R is canceled by the conveyance force F2. Is done.

  Accordingly, since the turning component R1 which is the basis for turning the sheet S is reduced, as shown in FIG. 5C, the sheet S is abutting reference member with a gentle posture without changing the posture extremely. It hits 71. As described above, in the case of FIG. 5 where the relationship “sheet length in the sheet conveyance direction = twice the distance D1” is satisfied, the effect of reducing the turning component R1 is the highest.

  Next, a case where the relationship of “sheet length in the sheet conveyance direction = twice the distance D1” is not generally satisfied, that is, a case where the nip position of the pre-slope feeding roller 12 is not on the center of gravity of the sheet S will be described. .

  At this time, as long as the skew feeding roller 70a is disposed at a position close to the abutting reference member 71 in order to prevent buckling at the time of abutting, the swirl component R1 is generated in almost all sizes.

  However, by positioning the pre-slope feeding roller 12 on the extension line in the sheet conveyance direction passing through the center of gravity of each sheet, the effect of reducing the swirl component R1 can be obtained with respect to a plurality of sheet sizes. That is, the movable unit 11U is moved, and the distance D2 (FIG. 2) may be controlled to a position that is approximately half the sheet length (size in the width direction of the sheet) in the direction perpendicular to the sheet conveyance direction.

  By the way, if the relationship of “the length in the sheet conveyance direction = twice the distance D1” can be established for the sheets having different lengths in the sheet conveyance direction, the turning component R1 can be reduced ideally. I can do it. Specifically, a second adjusting unit is provided separately to make it possible to move the positions of the pre-slope feeding roller 12 and the driven roller 12j in the sheet conveying direction, and it is half the length of the conveyed sheet S in the sheet conveying direction. Position to position. In other words, the distance D1 in the sheet conveyance direction from the nip of the skew feeding roller 70a to the nip of the pre-slope feeding roller 12 so that the pre-slope feeding roller 12 can start conveyance at a position half the length of the sheet S in the conveyance direction. Is made variable by the second adjusting means. As indicated by the broken line in FIG. 2, the pre-slope feeding roller 12 may be a second adjusting means that can change the distance between D1, D1 ',... And a plurality of values.

  According to the configuration of the first embodiment, since the turning component R1 acting on the sheet S can be reduced, the abutting angle of the sheet S with respect to the abutting reference member 71 can be moderated. For this reason, compared to Comparative Examples 1, 2, and 3 to be described later, since it can be prevented from hitting from the leading edge or the trailing edge of the sheet, it is caused by damage to the reference edge of the sheet or loss during the butting operation. Can be prevented. Thereby, compared with the configurations of Comparative Examples 1, 2, and 3, an effect of improving the media handling capability of the sheet conveying apparatus and the image forming apparatus can be obtained.

  Further, it is possible to contact the abutting reference member 71 in a substantially translated state while keeping the sheet conveying posture stable. For this reason, the interval between the skew feeding rollers 70 a, 70 b and 70 c including the receiving margin of the rotated sheet and the abutting reference member 71 can be set narrower than those of the first, second and third comparative examples. As a result, the abutting reference member 71 can be shortened, and the skew feeding registration device 65 can be reduced in size, and it is easy to cope with a weak sheet.

  Further, the skew feeding roller 70a (first skew feeding rotating body) and the pre-slope feeding roller 12 (second skew feeding rotating body) are positioned to the end and center of the sheet in the direction perpendicular to the sheet conveying direction, respectively. For this reason, even if the sheet size changes, the swirl component to rotate the sheet can be kept small.

  Note that the position of each sensor shown in FIG. 2 and the control timing shown in FIG. 4 are merely examples, and are not limited thereto.

  In addition, in the description, the notation related to the position such as “center of gravity” and “half” means that the position is an ideal position when considered based on the relationship of the force acting on the seat, and is limited. It doesn't mean. That is, in implementation, there is some deviation in the “center of gravity” and “half” positions due to variations in component tolerances and conveyance accuracy, but the effects of the present invention are not lost by these deviations.

  In the first embodiment, the pre-slope feeding roller 12 and the oblique feeding rollers 70a, 70b, and 70c are driven and the driven rollers 12j, 70i, 70j, and 70k are driven, but the relationship between the driving side and the driven side is as follows. It may be reversed. Then, the pre-slope feeding roller 12 and the slope feeding rollers 70a, 70b, 70c and the driven rollers 12j, 70i, 70j, 70k may all be driven.

  In the first embodiment, the sheet is nipped and conveyed between the pre-slope feeding roller 12 and the oblique feeding rollers 70a, 70b, and 70c and the driven rollers 12j, 70i, 70j, and 70k. However, the driven rollers 12j, 70i, 70j, and 70k may be replaced with flat surfaces with less friction. The pre-slope feeding roller 12 and the slope feeding rollers 70a, 70b, and 70c may be used as so-called friction rollers, and the opposite surfaces may be slid and rotated during idling.

  In the second and third embodiments to be described later, the description is not made avoiding duplication, but the same applies to these writings.

<Comparative Example 1>
FIG. 6 is a plan view of the skew feeding registration apparatus of the first comparative example, and FIG. 7 is an explanatory diagram of each stage of the conveyance control in the first comparative example. Since the skew feeding registration device 65E of the comparative example 1 is installed in place of the skew feeding registration device 65 shown in FIG. 1, the same reference numerals as those in FIG. Therefore, duplicate explanations are omitted.

  As shown in FIG. 6, the pre-registration conveyance unit 64 </ b> R conveys the sheet placed on the plane of the conveyance guide 75 with the pre-registration conveyance rollers 73 and 74 in the arrow A direction.

  The pre-registration conveyance unit 64R and the skew feeding registration unit 65P are central reference sheet conveyance apparatuses in which a conveyance reference is set on a center line along the sheet conveyance direction.

  The skew feeding registration unit 65P feeds the sheet S placed on the fixed conveyance guide 72 obliquely by the oblique feeding rollers 70a, 70b, and 70c that are installed at an angle α with respect to the sheet conveyance direction. The contact reference member 71 is brought into contact.

  The oblique feeding rollers 70a, 70b, and 70c feed the sheet S obliquely and press the sheet S against the abutting reference member 71 while moving the sheet S at a high speed in the conveying direction, and the sides of the sheet S are in line contact with the abutting reference member 71. Rotate the sheet until it is corrected. At this time, the nips of the upstream pre-registration conveyance rollers 73 and 74 are released so as not to disturb the oblique feeding by the oblique feeding rollers 70a, 70b, and 70c.

  As shown in FIG. 7 (a), the sheet S caught in the nip portion of the oblique feeding roller 70a receives the conveying force F3 from the oblique feeding roller 70a and is obliquely fed in the direction of the conveying force F3. Then, a resistance force R due to friction with the conveyance guide 75 acts on the center of gravity G of the sheet S in a direction opposite to the direction of the conveyance force F3.

  At this time, the resistance force R is broken down into a component force R2 that resists skew feeding and a component force (swivel component) R1 that tries to rotate the sheet S around the skew feeding roller 70a. Since the moment M due to the swirl component R1 rotates the conveyed sheet S, the abutting reference side of the sheet S is located at the edge E of the entrance of the abutting reference member 71 as shown in FIG. The possibility of contact comes out.

  In the comparative example 1, basically, the moment M is always generated in the state of FIG. 7A regardless of the sheet size. In particular, in the case of A4 size lateral feed or the like, as the length of the abutting reference side becomes a short edge shorter than the width direction of the sheet, the swirl component R1 becomes larger and an element that makes the sheet lighter is added. Damage of the sheet due to the problem becomes a problem. Unnecessary rotation of the sheet S is not limited to damage to the sheet, and may cause the occurrence of a conveyance jam, a decrease in side edge alignment accuracy, and a decrease in quality of a printed product.

<Comparative example 2>
FIG. 8 is an explanatory diagram of each stage of conveyance control in the skew feeding registration apparatus of the second comparative example. Since the skew feeding registration device 65F of the comparative example 2 is installed in place of the skew feeding registration device 65 shown in FIG. 1, the same reference numerals as those in FIG. Therefore, duplicate explanations are omitted.

  As shown in FIG. 8A, the skew feeding registration device 65F is configured to skew the sheet S placed on the fixed conveyance guide 72 with skew feeding rollers 80 and 81 installed to be inclined with respect to the conveyance direction. And is brought into contact with the abutting reference member 71.

  In Comparative Example 2, the distance x1 from the abutting reference member 71 to the oblique feeding roller 80 is larger than the distance x2 from the abutting reference member 71 to the oblique feeding roller 81.

  As shown in FIG. 8A, when the sheet S is engaged with the skew feeding roller 80, the turning component R1 of the resistance R due to friction with the conveyance guide 75 generates a moment M1, and the trailing edge of the sheet S Is swung to the abutting reference member 71 side.

  Thereafter, as shown in FIG. 8B, the sheet S is engaged with two of the oblique feeding rollers 80 and 81 in an inclined posture. Here, for the first time, the sheet S is positively brought into contact with the reference member 71 side. The moment M2 that approaches the target can be obtained.

  As a result, as shown in FIG. 8C, the sheet M is applied with the moment M3 so that the posture of the sheet S follows the abutting reference member 71 with the leading end abutted against the abutting reference member 71. To do.

  In the comparative example 2, the upstream side feeding roller 80 conveys the sheet S at a position close to the center of gravity of the sheet S due to the relationship of distance x1> distance x2, so that the turning component R1 can be made smaller than that in the comparative example 1. However, when the abutting reference side of the sheet S becomes a short edge as in A4 size lateral feed, the possibility that the sheet S contacts the abutting reference member 71 remains as shown in FIG. Yes.

  Further, only by the relationship of distance x1> distance x2, in the stage shown in FIG. 8A, the leading edge of the sheet S is rather moved away from the reference member 71. Therefore, the behavior of the sheet S from when the sheet S enters the skew feeding roller 80 until the skew correction is completed becomes very unstable in which the turning direction changes alternately.

<Comparative Example 3>
FIG. 9 is an explanatory diagram of each stage of conveyance control in the skew feeding registration apparatus of Comparative Example 3. Since the skew feeding registration device 65G of Comparative Example 3 is installed in place of the skew feeding registration device 65 shown in FIG. 1, the same reference numerals as those in FIG. Therefore, duplicate explanations are omitted.

  As shown in FIG. 9A, the skew feeding registration device 65G is configured to skew the sheet S placed on the fixed conveyance guide 72 with skew feeding rollers 91 and 92 installed to be inclined with respect to the conveyance direction. And is brought into contact with the abutting reference member 71.

  The skew feeding registration device 65G of Comparative Example 3 is a central reference sheet conveyance device in which a conveyance reference is set on a center line along the sheet conveyance direction. The skew feeding rollers 91 and 92 are arranged separately on both sides of the conveyance center 90 of the sheet S along the sheet conveyance direction. The upstream-side skew feeding roller 91 is disposed on the side far from the abutting reference member 71 with respect to the conveyance center 90, and the downstream-side oblique feeding roller 92 is near the abutting reference member 71 with respect to the conveyance center 90. Placed in.

  As shown in FIG. 9A, when the upstream feeding roller 91 bites the sheet S, the turning component R1 of the resistance force R acting on the center of gravity G of the sheet S abuts against the leading edge of the sheet S. A moment M1 that approaches the member 71 side is generated.

  As shown in FIG. 9B, when the two skew feeding rollers 91 and 92 bit the sheet S, the swirl component R1 of the resistance force R acting on the center of gravity G of the sheet S further pushes the leading edge of the sheet S. A moment M2 that approaches the abutting reference member 71 is generated.

  As a result, when the leading edge of the sheet S comes into contact with the abutting reference member 71, as shown in FIG. 9C, the posture is greatly skewed, and the side of the sheet S is lined with the abutting reference member 71. The rotation angle of the sheet S required until the contact is increased.

  In Comparative Example 3, the moments M1 and M2 are continuously applied only in the direction in which the leading end of the sheet S comes close to the abutting reference member 71 until the leading end of the sheet S abuts against the abutting reference member 71. Then, after the leading edge of the sheet S has abutted against the abutting reference member 71, the moment M3 in a direction in which the rear end side of the sheet S is brought close to the abutting reference member 71 is received.

  As a result, the behavior of the sheet S is more stable than that of the comparative example 2, and contact with the abutting reference member 71 as shown in FIG.

  However, the rotation angle of the sheet S until the leading end of the sheet S comes into contact with the abutting reference member 71 is larger than that in the second comparative example. The distance S1 shown in (b) of FIG. 9 gradually increases to the distance S2 shown in (c) of FIG.

  For this reason, in the skew correction stage after (c) in FIG. 9, there is a case where the moment M3 cannot be completely moved to the rear end of the sheet S. This problem becomes prominent when the frictional force between the conveyance guide 75 and the sheet S is large, or when the sheet S has a large basis weight represented by thick paper.

<Example 2>
FIG. 10 is a plan view of the skew feeding registration apparatus of the second embodiment. The skew feeding registration device 65B of the second embodiment is installed by replacing the skew feeding registration device 65 shown in FIG. 1, and therefore, in FIG. 10, the same reference numerals as those in FIG. Therefore, duplicate explanations are omitted.

  As shown in FIG. 10, the skew registration device 65 </ b> B receives the sheet conveyed in the direction of arrow A from the pre-registration conveyance rollers 73 and 74, corrects the skew, and transfers the sheet to the slide roller 7.

  The slide part 65R and the secondary transfer part 66P are basically the same as those in the first embodiment. The slide roller 7 slides in the direction of arrow B while holding the sheet, and aligns the thrust position of the sheet whose skew has been corrected in the skew feeding registration device 65B with the toner image on the intermediate transfer belt (606: FIG. 1). .

  The skew feeding registration device 65B feeds the sheet placed on the conveyance guide 72 obliquely by the skew feeding rollers 70a, 70b, and 70c and the pre-slope feeding roller 12, and slides the side edge of the sheet to the reference member 71. Align side edges.

  The sheet conveying apparatus including the skew feeding registration device 65B according to the second embodiment is a one-side reference sheet conveying apparatus having a conveyance reference on the front side (abutting reference member 71) of the apparatus. For this reason, if the sheet length (sheet width) in the direction perpendicular to the sheet conveying direction is different, the position of the center line of the sheet along the sheet conveying direction changes.

  In the skew feeding registration device 65B of the second embodiment, the transport guide 72 is a fixed type and is not divided into the fixed guide 10 and the movable guide 11 as in the first embodiment. Instead, the pre-conveying roller 12 and the driven roller (12j: FIG. 3) integrally move relative to each other in the direction perpendicular to the sheet conveying direction (arrow C direction), and according to the sheet size with the conveying guide 72. Set the distance. The opening 75h formed in the conveyance guide 75 shown in FIG. 3 is formed in a length corresponding to the movement stroke of the conveyance roller 12 and the driven roller 12j.

  The control unit (9: FIG. 3) controls the mechanism for moving the pre-conveying roller 12 and the driven roller (12j: FIG. 3) in the direction of arrow C, and pre-tilt the sheet on the center line of the sheet along the sheet conveying direction. The roller 12 is positioned and a sheet is awaited. The control unit (9: FIG. 3) determines that the distance D2 in the direction perpendicular to the sheet conveyance direction from the nip of the skew feeding rollers 70a, 70b, and 70c to the nip of the pre-slope feeding roller 12 is in the width direction of the conveyed sheet. The pre-slope feeding roller 12 is positioned so as to be half the length.

  Sheet skew correction by the pre-slope feeding roller 12 and the skew feeding rollers 70a, 70b, and 70c is basically as described in the first embodiment with reference to FIGS. As a different place, as described above, since the conveyance reference is the front (abutting reference member 71) side, the pre-slope feeding roller 12 is moved to a position satisfying the relationship of “distance D2 = half sheet width”. It is a point to wait.

  Therefore, with respect to the second embodiment, FIGS. 5A to 5C show the state after the pre-slope feeding roller 12 has moved to a predetermined position in accordance with the selection of the size of the conveyed sheet. I think that. The relationship between the forces acting on the sheet S and the nip attachment / detachment timing of the pre-slope feeding roller 12 are as described in the first embodiment.

  The distance in the sheet conveying direction from the nip of the skew feeding roller 70a to the nip of the pre-slope feeding roller 12 is also as described in the first embodiment with respect to being separated by the distance D1.

  That is, when the relationship “sheet length in the sheet conveyance direction = twice the distance D1” is established, the effect of reducing the turning component R1 is the highest. However, even if this relationship is not satisfied, if the skew feeding by the pre-slope feeding roller 12 is started at a position where the distance D2 becomes half the sheet width (on the line in the sheet conveying direction passing through the center of gravity G of the sheet), a plurality of sheets The effect of reducing the swirl component R1 is high with respect to the size.

  By the way, if the relationship of “the length in the sheet conveyance direction = twice the distance D1” can be established for the sheets having different lengths in the sheet conveyance direction, the turning component R1 can be reduced ideally. I can do it. Specifically, a second adjusting unit is provided separately to make it possible to move the positions of the pre-slope feeding roller 12 and the driven roller 12j in the sheet conveying direction, and it is half the length of the conveyed sheet S in the sheet conveying direction. Position to position. In other words, the distance D1 in the sheet conveyance direction from the nip of the skew feeding roller 70a to the nip of the pre-slope feeding roller 12 so that the pre-slope feeding roller 12 can start conveyance at a position half the length of the sheet S in the conveyance direction. Is made variable by the second adjusting means. Even if the second adjusting means is realized by a mechanism in which this distance can be varied between D1, D1 ′,... And a plurality of values, as indicated by the broken line in FIG. Good.

  According to the second exemplary embodiment, even when the conveyance reference is not the central reference as in the first exemplary embodiment, the effect of improving the media handling capability of the sheet conveying apparatus and the image forming apparatus can be obtained as in the first exemplary embodiment.

  Note that the sheet conveying apparatus shown in FIG. 10 is configured to perform the abutting operation toward the near side, so that the near side reference is used. However, the same is true for the back side reference having an abutting reference member toward the far side. An effect is obtained.

<Example 3>
FIG. 11 is a plan view of the skew feeding registration apparatus of the third embodiment. Since the skew feeding registration device 65C of the third embodiment is installed in place of the skew feeding registration device 65 shown in FIG. 1, the same reference numerals as those in FIG. Therefore, duplicate explanations are omitted.

  As shown in FIG. 11, the skew feeding registration device 65 </ b> C receives the sheet conveyed in the direction of arrow A from the pre-registration conveyance rollers 73 and 74, corrects the skew, and transfers the sheet to the slide roller 7.

  The slide part 65R and the secondary transfer part 66P are basically the same as those in the first embodiment. The slide roller 7 slides in the direction of arrow B while holding the sheet, and aligns the thrust position of the sheet whose skew has been corrected in the skew feeding registration device 65C with the toner image on the intermediate transfer belt (606: FIG. 1). .

  The pre-registration conveyance unit 64R and the skew feeding registration unit 65P according to the third exemplary embodiment are central reference sheet conveyance apparatuses in which a conveyance reference is set on a center line along the sheet conveyance direction.

  The skew feeding registration device 65C of the third embodiment is configured in the same manner as in the first embodiment, and obliquely feeds the sheet sent to the movable guide 11 and the fixed guide 10 of the movable unit 11U, and sets the side edge of the sheet as a reference member. The side end is aligned by sliding on 71.

  The movable unit 11U moves in the arrow C direction and stands by in accordance with the size of the conveyed sheet. The movable unit 11U is configured so that a distance D2 in a direction orthogonal to the sheet conveying direction from the nip of the skew feeding rollers 70a, 70b, and 70c to the nip of the pre-slope feeding roller 12 is half the sheet width of the conveyed sheet. Positioning is controlled.

  In the third embodiment, a plurality of pre-slope feeding rollers 12, 13, and 14 configured to be individually movable up and down are arranged on the center line (conveyance reference) of the pre-registration conveyance unit 64R. The plurality of pre-slope feeding rollers 12, 13, and 14 are arranged so that the distance in the sheet conveyance direction from each nip portion to the nip portion of the slope feeding roller 70a is a distance D1, D1 ′, D1 ″. Yes. Thereby, the pre-slope feeding rollers 12, 13, and 14 can contact the sheet surface at different positions in the sheet conveying direction.

  The distances D1, D1 ′, and D1 ″ correspond to different sizes, for example, half the length in the transport direction of A4, A4R, and A3 size sheets, and correspond to the center of gravity of the transported sheet. Select and use properly.

  Specifically, each of the pre-slope feeding rollers 12, 13, and 14 as an example of the second adjusting unit includes a nip releasing mechanism. The control unit (9: FIG. 3) selects the optimum pre-slope feeding roller according to the sheet size data of the conveyed sheet, that is, the pre-slope feeding roller capable of nipping on the center of gravity of the sheet to form a nip. Let

  Sheet skew correction by the pre-slope feeding rollers 12, 13, 14 and the skew feeding rollers 70a, 70b, 70c is basically the same as that described in the first embodiment with reference to FIGS. The difference is that, as described above, the optimum one is selected from the plurality of pre-slope feeding rollers 12, 13, and 14, and the sheet is conveyed. Therefore, in the third embodiment, during the description of the first embodiment, the pre-slope feeding roller 12 may be the pre-slope feeding roller 13 or the pre-slope feeding roller 14 depending on the sheet size. However, the relationship between the forces acting on the sheet S and the nip attachment / detachment timing of the selected pre-slope feeding rollers 12, 13, and 14 are the same as those in the first embodiment.

  According to the configuration of the third embodiment, since the ideal reduction of the turning component R1 can be expected for a plurality of sizes, a smooth abutting operation with respect to the abutting reference member 71 can be realized with a larger size. FIG. 11 shows an example in which three pre-slope feeding rollers are arranged, but by increasing the number to three or more, it is possible to cope with a finer sheet size difference.

  In addition, a minimum number of pre-slope feeding rollers that can handle the main sheet sizes are provided, and in the case of non-standard sizes, a pre-slope feeding roller that can form a nip closest to the center of gravity of the sheet is selected. However, the effect of reducing the turning component R1 can be sufficiently obtained.

  Although the sheet conveying apparatus shown in FIG. 11 is based on the central reference, a single-side reference sheet conveying apparatus as in the second embodiment can be similarly controlled by arranging a plurality of pre-slope feeding rollers. is there. In this case, as described in the second embodiment, it is necessary to separately provide a mechanism for allowing the plurality of pre-slope feeding rollers to move in a direction orthogonal to the sheet conveying direction.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment. FIG. 3 is a plan view of a transport unit including the skew feeding registration apparatus according to the first exemplary embodiment. It is explanatory drawing of the drive mechanism of a skew feeding registration apparatus. It is a flowchart of conveyance control. It is explanatory drawing of each step of conveyance control. 7 is a plan view of a skew feeding registration apparatus of Comparative Example 1. FIG. 10 is an explanatory diagram of each stage of conveyance control in Comparative Example 1. FIG. It is explanatory drawing of each step | level of the conveyance control in the skew feeding registration apparatus of the comparative example 2. It is explanatory drawing of each step | level of the conveyance control in the skew feeding registration apparatus of the comparative example 3. FIG. FIG. 6 is a plan view of a skew feeding registration apparatus according to a second embodiment. 6 is a plan view of a skew feeding registration apparatus according to Embodiment 3. FIG.

Explanation of symbols

7 Slide roller 9 Control means (control unit)
11U, 72 Transport path (movable unit, transport guide)
12 Second skew feeding rotating body (pre-slope feeding roller)
13, 14 Second adjusting means (pre-slope feeding roller)
61 Paper Feeding Device 63 Paper Feeding Unit 65 Sheet Conveying Device (Slave Feeding Registration Device)
71 Reference member (butting reference member)
70a, 70b, 70c First skew feeding rotating body (slope feeding roller)
66P, 606 Image forming means (secondary transfer unit, intermediate transfer belt)
601 Reverse conveyance device 603 Secondary transfer inner roller 608 Photoconductor 609 Photoconductor cleaner 610 Development device 611 Exposure device 613 Image forming unit A Sheet conveyance direction (arrow A)
M1 first adjusting means (motor)
S sheet

Claims (5)

A reference member that is arranged along the sheet conveying direction and aligns the sheet by sliding contact with the sheet;
A first obliquely rotating body that rotates in contact with the sheet and obliquely feeds the sheet toward the reference member;
Arranged upstream of the first skew feeding rotator and farther from the reference member than the first skew feeding rotator, corresponding to the center position of the sheet in a direction perpendicular to the sheet conveying direction, A second inclined feeding rotating body that rotates in contact with the sheet and obliquely feeds the sheet toward the reference member;
A contact / separation mechanism for contacting and separating the second skew feeding rotary body from the sheet,
The second skew feeding rotator is brought into contact with the sheet at a timing when the sheet conveyed in the sheet conveying direction with the second skew feeding rotator separated from the sheet reaches the first skew feeding rotator. The sheet conveying apparatus is characterized in that the contact / separation mechanism is controlled as described above. A first adjusting means for adjusting a distance between the second skew feeding rotary member and the reference member in a direction perpendicular to the sheet conveying direction;
2. The sheet conveying apparatus according to claim 1, wherein the second skew feeding rotary member is moved to the center of the sheet in a direction perpendicular to the sheet conveying direction according to the size of the sheet being conveyed. A second adjusting means for adjusting a distance between the second skew feeding rotary member and the reference member in the sheet conveying direction;
3. The sheet conveying apparatus according to claim 2, wherein the second skew feeding rotary member is moved to the center of the sheet in the sheet conveying direction according to the size of the sheet being conveyed. The second adjusting means arranges the plurality of second oblique feeding rotators at different positions in the sheet conveying direction,
4. The sheet conveying apparatus according to claim 3, wherein one sheet is selected according to the size of the sheet conveyed from the plurality of second obliquely rotating bodies so as to be in contact with the sheet. Image forming means for forming an image on a sheet;
An image forming apparatus comprising: the sheet conveying apparatus according to claim 1, which feeds a sheet to the image forming unit.

Images